1. Field of the Invention
The invention is related to the field of gearing. More particularly, the invention is related to the field of sectional rotary bodies. In still greater particularity, the invention is a backlash take-up device. By way of further characterization, but not by way of limitation thereto, the invention is a device for applying a lateral force to a driving nut in order to maintain intimate contact between the threads of the driving nut and the threads of a rotating shaft.
2. Description of the Prior Art
Backlash, a common problem with any ordinary drive mechanism, is mainly due to dimensional clearance between mating components. The performance and accuracy of a drive mechanism is related to, and limited by, the amount of backlash within the mechanism. It is not only impractical, but also prohibitively costly, to perfectly match every component within every drive mechanism to achieve zero backlash. There are numerous anti-backlash drive mechanism designs in existence today. Many of these devices load the drive nuts which are threaded onto the lead screw in order to maintain thread contact between the drive nuts and lead screws. This loading is done in an axial direction. For example, one such device disclosed in U.S. Pat. No. 4,279,173 issued to F. G. Krebs et al. on July 21, 1981 discloses such a device. That is, Krebs employs a spring loaded split nut to accomplish zero backlash. The pre-loading force is supplied by a spring and is applied vertically to the nuts such that force is exerted in opposite directions on the lead screw. The rotation of the lead screw tends to wind and unwind the spring loading apparatus. In clinical laboratory instruments such as diluters on dispensers, precise amounts of liquids must be dispensed. That is, in a clinical assay the volume ratios are critical to the accuracy of the test being performed. Thus, precise movement of the driving mechanism is required in order to displace these precise volumes. While the above described types of anti-backlash mechanisms are suited for their intended purposes, they tend to be costly and complicated. These devices require a separate guide rod and anti-rotation devices.